Use Sphinx for documentation

See #60

docs/overview.rst

@@ -0,0 +1,26 @@
+Overview
+========
+
+As far as I know, sshuttle is the only program that solves the following
+common case:
+
+- Your client machine (or router) is Linux, FreeBSD, or MacOS.
+
+- You have access to a remote network via ssh.
+
+- You don't necessarily have admin access on the remote network.
+
+- The remote network has no VPN, or only stupid/complex VPN
+  protocols (IPsec, PPTP, etc). Or maybe you *are* the
+  admin and you just got frustrated with the awful state of
+  VPN tools.
+
+- You don't want to create an ssh port forward for every
+  single host/port on the remote network.
+
+- You hate openssh's port forwarding because it's randomly
+  slow and/or stupid.
+
+- You can't use openssh's PermitTunnel feature because
+  it's disabled by default on openssh servers; plus it does
+  TCP-over-TCP, which has terrible performance (see below).